Peugeot's parent company, PSA Peugeot Citroen, has been working for a while on a drivetrain that would hybridize a conventional engine with compressed air rather than batteries. The powertrain would include a hydraulic pump that allows the car to run in all-gasoline, all-air or combined modes, which is where the name "Hybrid Air" comes from. Peugeot now says its compressed air hybrid powertrain can get almost 100 miles per gallon and one that's built into a Peugeot 208 hatchback will start rolli